Objective lens and environmental scanning electron microscope

Abstract

The application relates to the technical field of electron microscopic imaging, and provides an objective lens and an environmental scanning electron microscope. The objective lens comprises at least: an upper pole shoe having a connecting portion and a working portion, the working portion is provided with a hollow accommodating cavity, and the working portion is suitable for forming an electron beam channel; a lower pole shoe connected with the connecting portion, and the working portion is at least partially inserted into the lower pole shoe, a region between an inner side wall of the lower pole shoe and an outer side wall of the working portion forms a transition vacuum area; a first air exhaust hole is arranged on a side wall of the lower pole shoe, and the transition vacuum area is suitable for being vacuumized through the first air exhaust hole; a sealing structure is arranged at one end of the lower pole shoe away from the upper pole shoe, so as to separate the electron beam channel from the transition vacuum area, and separate the transition vacuum area from an external environment; the sealing structure is provided with a gas channel and a first through hole through which an electron beam passes, and the gas channel is communicated with the first through hole and the transition vacuum area. The objective lens is more convenient to maintain high vacuum degree of the electron beam channel in a scanning process, so that the scanning effect is improved.

Description

Technical Field

[0001] This invention relates to the field of electron microscopy imaging technology, specifically to an objective lens and an environmental scanning electron microscope. Background Technology

[0002] Scanning Electron Microscopy (SEM) is a high-resolution microscopic instrument used for characterizing and analyzing the microstructure of samples, and it has gradually become an essential tool for technological research and development in many fields. The objective lens is the core focusing component of SEM, generally composed of an excitation current coil, an iron shell, and pole pieces. The iron shell and pole pieces together constitute the magnetic circuit. The objective lens generates a strong magnetic field through the excitation current coil, and the distribution of this strong magnetic field is adjusted through the magnetic circuit structure. The pole piece structure of the objective lens allows the strong magnetic field to be concentrated near the pole pieces, thereby achieving the final focusing of the electron beam. This reduces and focuses the electron beam onto the sample surface at a short working distance. Based on the characteristics of objective lens imaging, reducing the working distance of the objective lens (the distance from the pole pieces to the sample under the objective lens) can effectively improve the SEM imaging resolution.

[0003] The objective lens is a key component for achieving high-resolution imaging in SEM. To ensure the transmission and performance of the electron beam and to give the objective lens high resolution, a high vacuum (typically better than 10) is required in the electron beam channel at the objective lens pole piece. - 3 However, when the observed sample contains a large amount of liquid, such as hydrated materials, biological tissues, and plant materials, a low pressure in the working chamber can easily alter the sample properties. Therefore, to ensure scanning results, the pressure in the working chamber needs to be controlled within a range greater than 610 Pa (saturated water vapor partial pressure at 0°C). However, at this point, the vacuum difference between the electron beam channel and the working chamber will be significant. Under these circumstances, general SEMs will find it difficult to maintain a high vacuum in the electron beam channel, which will severely affect electron beam scanning imaging. Therefore, to make scanning electron microscopy more widely applicable to various types of samples, it is necessary to maintain a sufficiently low vacuum in the working chamber to preserve the properties and morphological characteristics of hydrated materials, biological tissues, and plant materials to be observed, while maintaining a high vacuum environment inside the objective lens to ensure that gas molecules do not excessively interfere with the quality of the electron beam. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that when the working environment pressure of a conventional SEM exceeds 610 Pa, the electron beam channel will be in a low vacuum state, making it impossible to achieve high-resolution sample observation. Thus, the present invention provides an objective lens and an environmental scanning electron microscope.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] An objective lens includes at least: an upper pole piece having a connecting portion and a working portion, the working portion having a hollow receiving cavity adapted to form an electron beam channel; a lower pole piece connected to the connecting portion, with the working portion at least partially inserted into the lower pole piece, a transition vacuum region being formed between the inner sidewall of the lower pole piece and the outer sidewall of the working portion; a first evacuation port provided on the sidewall of the lower pole piece, adapted to evacuate the transition vacuum region through the first evacuation port; a sealing structure disposed at the end of the lower pole piece away from the upper pole piece, to separate the electron beam channel from the transition vacuum region and to isolate the transition vacuum region from the external environment; the sealing structure having a gas channel and a first through-hole for the electron beam to pass through, the gas channel connecting the first through-hole and the transition vacuum region.

[0007] Furthermore, a gap is left between the end of the working part away from the connecting part and the inner wall of the lower pole shoe to connect the transition vacuum zone and the gas channel.

[0008] Furthermore, the sealing structure includes a sealing ring and a plugging member; one end of the sealing ring is inserted into the receiving cavity, and the other end abuts against the inner bottom wall of the lower pole shoe; the gas passage is provided on the sealing ring; a second through hole is provided at the bottom of the lower pole shoe; a groove is provided on the end face of the sealing ring facing the second through hole, and the groove penetrates the other end face of the sealing ring along the height direction of the sealing ring; the plugging member is inserted into the groove through the second through hole, and the first through hole is provided on the plugging member.

[0009] Furthermore, the sealing member includes a connected cap body and a plug portion; the first through hole passes through the cap body and the plug portion sequentially along the height direction of the sealing member; the plug portion is inserted into the groove through the second through hole; the cap body is located outside the lower pole shoe and abuts against the outer bottom wall of the lower pole shoe.

[0010] Furthermore, a first sealing ring is provided between the cap body and the outer bottom wall of the lower pole shoe.

[0011] Furthermore, a second sealing ring is provided between the outer wall of the sealing ring and the inner wall of the receiving cavity.

[0012] Furthermore, the objective lens also includes an electron beam tube inserted into the receiving cavity, with the end of the electron beam tube located in the receiving cavity extending into the groove, and the lumen of the electron beam tube forming the electron beam channel; along the irradiation direction of the electron beam, the lumen of the electron beam tube is collinear with the first through hole.

[0013] Furthermore, a third sealing ring is provided between the outer wall of the electron beam tube and the groove wall of the groove.

[0014] Furthermore, the objective lens also includes a kit and a vacuum tube; the kit is fitted over the outside of the lower pole shoe, and the open edge of the kit is connected to the open edge of the lower pole shoe by bolts; a second evacuation port is provided on the side wall of the kit at a position corresponding to the first evacuation port, one end of the vacuum tube is connected to the second evacuation port, and the other end is adapted to be connected to an external vacuum pump.

[0015] Furthermore, a fourth sealing ring and a fifth sealing ring are provided between the inner sidewall of the kit and the outer sidewall of the lower pole shoe, and the fourth sealing ring and the fifth sealing ring are respectively located on different sides of the second air extraction hole along the height direction of the kit.

[0016] Furthermore, the objective lens also includes a support, a frame, and a coil; the support has a ring-shaped structure and is fitted onto the working part; the inner ring of the support abuts against the outer wall of the working part, and the outer ring of the support abuts against the inner wall of the lower pole shoe; the area between the side of the support facing the sealing structure, the inner wall of the lower pole shoe, and the outer wall of the working part forms the transition vacuum zone; the frame is fitted onto the working part, and the frame abuts against the side of the support facing away from the sealing structure; the coil is arranged on the frame circumferentially.

[0017] Furthermore, a sixth sealing ring is provided between the inner ring of the bracket and the outer side wall of the working part; a seventh sealing ring is provided between the outer ring of the bracket and the inner side wall of the lower pole shoe.

[0018] Furthermore, the objective lens also includes a water-cooling structure, including an adapter, an inlet pipe, and an outlet pipe; one end of the inlet pipe is connected to the water inlet of the skeleton, and the other end is connected to an external cooling water source through the adapter; one end of the outlet pipe is connected to the water outlet of the skeleton, and the other end is connected to an external cooling water source through the adapter.

[0019] An environmental scanning electron microscope, comprising at least the objectives described above.

[0020] Furthermore, the environmental scanning electron microscope further includes at least: a working chamber, on the side wall of which a third evacuation port and a fourth evacuation port are provided; the objective lens extends at least partially into the working chamber, and the vacuum channel on the objective lens is connected to the fourth evacuation port via a pipe; and a worktable, disposed in the working chamber and located below the objective lens.

[0021] The technical solution of this invention has the following advantages:

[0022] The objective lens provided by this invention forms a transition vacuum region between the upper and lower pole shoes. A sealing structure separates the electron beam channel from the transition vacuum region and also isolates the transition vacuum region from the external environment. A gas channel connects the transition vacuum region to the electron beam channel. In use, the vacuum level of the transition vacuum region is maintained within a suitable range through the first evacuation port, ensuring that the vacuum level of the transition vacuum region is between that of the electron beam channel and the working chamber. This configuration effectively creates a buffer zone with a vacuum level between the higher vacuum level of the electron beam channel and the lower vacuum level of the working chamber. Furthermore, because the vacuum difference between the electron beam channel and the transition vacuum region is small, even when the ambient pressure in the working chamber exceeds 610 Pa, it is easier to maintain a high vacuum level in the electron beam channel during scanning, enabling high-resolution sample observation and thus improving scanning performance. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of the objective lens in an embodiment of the present invention;

[0025] Figure 2 for Figure 1 A sectional view;

[0026] Figure 3 for Figure 2 A magnified schematic diagram of a local structure;

[0027] Figure 4 This is a schematic diagram of the upper pole shoe in the objective lens of an embodiment of the present invention from one angle.

[0028] Figure 5 This is a schematic diagram from another perspective of the upper pole shoe in the objective lens in an embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of the lower pole shoe in the objective lens in an embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of the electron beam tube in the objective lens in an embodiment of the present invention;

[0031] Figure 8 This is a schematic diagram of the kit in the objective lens according to an embodiment of the present invention;

[0032] Figure 9This is a schematic diagram of the sealing ring in the objective lens in an embodiment of the present invention;

[0033] Figure 10 This is a schematic diagram of the sealing element in the objective lens in an embodiment of the present invention;

[0034] Figure 11 for Figure 10 A schematic diagram of a cross-sectional view;

[0035] Figure 12 This is a schematic diagram of the support in the objective lens according to an embodiment of the present invention;

[0036] Figure 13 This is a schematic diagram of the coil and frame in the objective lens of an embodiment of the present invention;

[0037] Figure 14 This is a schematic diagram of the cooling structure in the objective lens in an embodiment of the present invention;

[0038] Figure 15 This is a partial structural schematic diagram of an environmental scanning electron microscope in an embodiment of the present invention;

[0039] Figure 16 This is a schematic diagram of the upper and lower pole shoes in an environmental scanning electron microscope according to an embodiment of the present invention.

[0040] 1. Objective lens; 2. Upper pole shoe; 3. Lower pole shoe;

[0041] 4. Kit; 5. Electron beam tube; 6. Water-cooled structure;

[0042] 7. Sealing structure; 8. Support; 9. Frame;

[0043] 10. Coil; 11. Electron beam channel; 12. Transition vacuum region;

[0044] 13. Receiving cavity; 14. Vacuum pipe; 15. First evacuation port;

[0045] 16. Second vent; 17. Third vent; 18. Fourth vent;

[0046] 19. First through hole; 20. Second through hole; 21. Connecting part;

[0047] 22. Working part; 23. Sealing ring; 24. Sealing component;

[0048] 25. First sealing ring; 26. Second sealing ring; 27. Third sealing ring;

[0049] 28. Fourth sealing ring; 29. ​​Fifth sealing ring; 30. Sixth sealing ring;

[0050] 31. Seventh sealing ring; 32. Inlet; 33. Outlet;

[0051] 34. Inlet pipe; 35. Outlet pipe; 36. Adapter;

[0052] 37. Insertion part; 38. Airflow hole; 39. Groove;

[0053] 40. Gas passage; 41. Working chamber; 42. Workbench;

[0054] 43. Notch; 44. First aperture plate; 45. Second aperture plate;

[0055] 46. ​​Third through hole. Detailed Implementation

[0056] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0058] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] Figure 1 This is a schematic diagram of the overall structure of the objective lens in an embodiment of the present invention; Figure 2 for Figure 1 A sectional view; Figure 3 for Figure 2 A magnified schematic diagram of a local structure; Figure 4 This is a schematic diagram of the upper pole shoe in the objective lens of an embodiment of the present invention from one angle. Figure 5 This is a schematic diagram of the upper pole shoe in the objective lens of an embodiment of the present invention from another perspective; as shown... Figure 1 , Figure 2 , Figure 3 , Figure 4 as well as Figure 5 As shown, this embodiment provides an objective lens 1, which includes at least: an upper pole piece 2, having a connecting portion 21 and a working portion 22. The working portion 22 has a hollow receiving cavity 13, suitable for forming an electron beam channel 11. For example, the upper pole piece 2 can be a concentric sleeve-like structure, with the inner sleeve serving as the working portion 22 and the outer sleeve serving as the connecting portion 21. Moreover, the length of the working portion 22 can be greater than the length of the connecting portion 21, and the distal end of the working portion 22 can be tapered.

[0061] Figure 6 This is a schematic diagram of the lower pole shoe in the objective lens of an embodiment of the present invention; as shown. Figure 6 As shown, the lower pole shoe 3 is connected to the connecting part 21. For example, the lower pole shoe 3 can have a funnel-shaped structure. The open edge of the lower pole shoe 3 can be connected to the upper pole shoe 2 by threads, and the contact surface between the two can be sealed by a sealing ring. The working part 22 is at least partially inserted into the lower pole shoe 3, and the area between the inner wall of the lower pole shoe 3 and the outer wall of the working part 22 forms a transition vacuum zone 12.

[0062] The lower pole shoe 3 has a first evacuation port 15 on its side wall, which can be used to evacuate the transition vacuum zone 12. For example, the pressure in the transition vacuum zone 12 can be controlled at 10. -2 Pa-10 -1 Pa.

[0063] A sealing structure 7 is located at the end of the lower pole shoe 3 furthest from the upper pole shoe 2 to separate the electron beam channel 11 from the transition vacuum region 12 and to isolate the transition vacuum region 12 from the external environment. The sealing structure 7 has a gas channel 40 and a first through hole 19 through which the electron beam passes. The gas channel 40 connects the first through hole 19 and the transition vacuum region 12. In use, the vacuum level of the transition vacuum region 12 is maintained between the vacuum level of the electron beam channel 11 and the vacuum level of the working chamber 41 through the first evacuation hole 15. This allows the vacuum level of the electron beam channel 11 to be maintained at a higher range more easily without changing the vacuum level of the working chamber 41.

[0064] The objective lens 1 provided in this embodiment forms a transition vacuum region 12 between the upper pole piece 2 and the lower pole piece 3. A sealing structure 7 separates the electron beam channel 11 from the transition vacuum region 12 and isolates the transition vacuum region 12 from the external environment. A gas channel 40 connects the transition vacuum region 12 to the electron beam channel 11. In use, the vacuum level of the transition vacuum region 12 is maintained within a suitable range through the first evacuation port 15, ensuring that the vacuum level of the transition vacuum region 12 is between that of the electron beam channel 11 and the working chamber 41. This configuration effectively creates a buffer zone with a vacuum level between the higher vacuum level of the electron beam channel 11 and the lower vacuum level of the working chamber 41. Furthermore, since the vacuum levels between the electron beam channel 11 and the transition vacuum region 12, and between the transition vacuum region and the working chamber, can be adjusted by changing the aperture to achieve the required pressure difference, even when the ambient pressure in the working chamber exceeds 610 Pa, it is easier to maintain a high vacuum level in the electron beam channel 11 during scanning, enabling high-resolution sample observation and improving scanning performance.

[0065] In this design, a notch 43 is left between the end of the working part 22 away from the connecting part 21 and the inner wall of the lower pole shoe 3 to connect the transition vacuum region 12 and the gas channel 40. Moreover, in order to control the airflow in the transition vacuum region 12 and the electron beam channel 11, an air resistance aperture can be placed in the gas channel 40 to change the air resistance of the gas channel 40.

[0066] Figure 9 This is a schematic diagram of the sealing ring in the objective lens in an embodiment of the present invention; Figure 10 This is a schematic diagram of the sealing element in the objective lens according to an embodiment of the present invention; as shown. Figure 9 and Figure 10 As shown, the sealing structure 7 includes a sealing ring 23 and a sealing element 24; one end of the sealing ring 23 is inserted into the receiving cavity 13, and the other end abuts against the inner bottom wall of the lower pole shoe 3. For example, the outer side wall of the sealing ring 23 can be set to fit as close as possible to the inner side wall of the receiving cavity 13 to improve the sealing performance.

[0067] The gas channel 40 is provided on the sealing ring 23. For example, the gas channel 40 can be provided along the radial direction of the sealing ring 23, and the number of gas channels 40 is not limited to one.

[0068] The bottom of the lower pole shoe 3 is provided with a second through hole 20, and the end face of the sealing ring 23 facing the second through hole 20 is provided with a groove 39. The groove 39 penetrates the other end face of the sealing ring 23 along the height direction of the sealing ring 23. The sealing member 24 is inserted into the groove 39 through the second through hole 20. For example, the outer side wall of the sealing member 24 is as close as possible to the inner side wall of the groove 39 to improve the sealing performance.

[0069] The first through hole 19 is provided on the sealing member 24. For example, the first through hole 19 is provided along the irradiation direction of the electron beam, that is, the gas channel 40 and the channel of the first through hole 19 can be provided perpendicularly.

[0070] The sealing component 24 includes a connected cap and a plug-in portion 37; for example, the cap can be a circular plate structure, and the plug-in portion 37 can be a columnar structure. A first through hole 19 passes through the cap and the plug-in portion 37 sequentially along the height direction of the sealing component 24; the plug-in portion 37 is inserted into a groove 39 through a second through hole 20; the cap is located outside the lower pole shoe 3 and abuts against the outer bottom wall of the lower pole shoe 3, for example, the cap and the lower pole shoe 3 can be fixed together by screws.

[0071] A first sealing ring 25 is provided between the cap body and the outer bottom wall of the lower pole shoe 3. For example, an annular groove can be provided on the side of the cap body facing the lower pole shoe 3, and the first sealing ring 25 can be placed in the annular groove to limit the first sealing ring 25 and prevent it from moving back and forth. Then, the cap body is pressed tightly against the lower pole shoe 3 so that the first sealing ring 25 seals the gap between the cap body and the lower pole shoe 3.

[0072] A second sealing ring 26 is provided between the outer wall of the sealing ring 23 and the inner wall of the receiving cavity 13. For example, an annular groove can be provided on the outer wall of the sealing ring 23 to place the second sealing ring 26 in the annular groove, thereby limiting the second sealing ring 26 and preventing it from moving back and forth.

[0073] Figure 7 This is a schematic diagram of the electron beam tube in the objective lens of an embodiment of the present invention; as shown. Figure 7 As shown, the objective lens 1 also includes an electron beam tube 5, which is inserted into the receiving cavity 13. The end of the electron beam tube 5 located in the receiving cavity 13 extends into the groove 39. The lumen of the electron beam tube 5 forms an electron beam channel 11. For example, the groove 39 can be a stepped groove. The groove opening on the side of the groove 39 facing the electron beam tube 5 is larger, and the groove opening on the side of the groove 39 facing the sealing member 24 is smaller, to prevent the electron beam tube 5 from extending out from the other side of the sealing ring 23. Along the irradiation direction of the electron beam, the lumen of the electron beam tube 5 is collinear with the first through hole 19 to ensure that the electron beam can be emitted from the objective lens 1.

[0074] The area between the electron beam tube 5 and the receiving cavity 13 can be used to install deflectors, astigmatism correction devices, and other components to improve electron beam performance.

[0075] A third sealing ring 27 is provided between the outer wall of the electron beam tube 5 and the groove wall of the groove 39. For example, an annular groove can be provided in the groove wall of the groove 39 to place the third sealing ring 27 in the annular groove, thereby limiting the third sealing ring 27 and preventing it from moving back and forth. The provision of the second sealing ring 26 and the third sealing ring 27 can effectively separate the electron beam channel 11 from the excessive vacuum area, so that the gas between the two can only flow through the flow channel formed by the first through hole 19, the gas channel 40 and the notch 43.

[0076] Figure 8 This is a schematic diagram of the kit in the objective lens according to an embodiment of the present invention; as shown. Figure 8 As shown, the objective lens 1 also includes a kit 4 and a vacuum tube 14. For example, the kit 4 can be frustoconical in shape and is fitted over the lower pole shoe 3, allowing for a better fit. The open edge of the kit 4 is connected to the open edge of the lower pole shoe 3 by bolts. A second evacuation port 16 is provided on the side wall of the kit 4 at a position corresponding to the first evacuation port 15. One end of the vacuum tube 14 is connected to the second evacuation port 16, and the other end is adapted to be connected to an external vacuum pump.

[0077] A fourth sealing ring 28 and a fifth sealing ring 29 are provided between the inner wall of the kit 4 and the outer wall of the lower pole shoe 3, and are spaced apart along the height of the kit 4. For example, to improve the sealing effect, the fourth sealing ring 28 can be located above the second vent 16, and the fifth sealing ring 29 can be located below the second vent 16. Similarly, an annular groove can be provided at a corresponding position on the inner wall of the kit 4 to limit the fourth sealing ring 28 and the fifth sealing ring 29.

[0078] Figure 12 This is a schematic diagram of the support in the objective lens according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the coil and frame in the objective lens of an embodiment of the present invention; as shown. Figure 12 and Figure 13 As shown, the objective lens 1 also includes a support 8, a frame 9, and a coil 10; the support 8 has a ring-shaped structure and is fitted onto the working part 22; the inner ring of the support 8 abuts against the outer wall of the working part 22, and the outer ring of the support 8 abuts against the inner wall of the lower pole shoe 3. The area between the side of the support 8 facing the sealing structure 7, the inner wall of the lower pole shoe 3, and the outer wall of the working part 22 forms a transition vacuum region 12; the frame 9 is fitted onto the working part 22, and the frame 9 abuts against the side of the support 8 facing away from the sealing structure 7; the coil 10 is arranged on the frame 9 along the circumference of the frame 9.

[0079] A sixth sealing ring 30 is provided between the inner ring of the bracket 8 and the outer wall of the working part 22; a seventh sealing ring 31 is provided between the outer ring of the bracket 8 and the inner wall of the lower pole shoe 3. For example, an annular groove can be provided at a corresponding position on the inner ring sidewall of the bracket 8 to limit the sixth sealing ring 30. For example, an annular groove can be provided at a corresponding position on the outer ring sidewall of the bracket 8 to limit the seventh sealing ring 31.

[0080] Figure 14 This is a schematic diagram of the cooling structure in the objective lens of an embodiment of the present invention; as shown. Figure 14 As shown, the objective lens 1 also includes a water-cooling structure 6, comprising an adapter 36, a water inlet pipe 34, and a water outlet pipe 35. One end of the water inlet pipe 34 is connected to the water inlet 32 ​​of the frame 9, and the other end is connected to an external cooling water source via the adapter 36. One end of the water outlet pipe 35 is connected to the water outlet 33 of the frame 9, and the other end is connected to an external cooling water source via the adapter 36. For example, a cooling cavity can be provided inside the frame 9. Cooling water enters the cooling cavity from the water inlet 32 ​​of the frame 9, absorbs heat, and then flows out of the cooling cavity from the water outlet 33 of the frame 9. With this configuration, the heat generated by the coil 10 is carried away by the circulating constant-temperature water flow, thereby maintaining the operating temperature of the objective lens 1, thus maintaining the stability of the objective lens 1 and reducing external interference that affects the high-performance operation of the electron beam.

[0081] Figure 15 This is a partial structural diagram of an environmental scanning electron microscope in an embodiment of the present invention, as shown below. Figure 15 As shown, another embodiment also provides an environmental scanning electron microscope, which includes at least the objective lens 1 described above.

[0082] The environmental scanning electron microscope includes at least a working chamber 41, on which a third evacuation port 17 and a fourth evacuation port 18 are provided on the side wall; for example, the working chamber 41 can be evacuated by connecting the third evacuation port 17 to an external vacuum pump through a pipeline.

[0083] In this configuration, the objective lens 1 extends at least partially into the working chamber 41. The vacuum channel 14 on the objective lens 1 is connected to the fourth evacuation port 18 via a conduit. A vacuum pump evacuates the transition vacuum zone 12; for example, the pressure within the working chamber 41 can be between 133 Pa and 1000 Pa. The difference in vacuum level between the transition vacuum zone 12 and the working chamber 41 is relatively small, making it easier to maintain the required vacuum level. Similarly, the difference in vacuum level between the electron beam channel 11 and the transition vacuum zone 12 is also relatively small, making it easier to maintain the required vacuum level, thus improving scanning performance. For example, the pressure within the electron beam channel 11 can be less than 10 Pa. -3 Pa.

[0084] The worktable 42 is located inside the working chamber 41 and below the objective lens 1, and is used to place the sample to be scanned.

[0085] In this application, both the upper pole shoe 2 and the lower pole shoe 3 can be made of high magnetic permeability materials. For example, DT4C can be used as the material for making the upper pole shoe 2 and the lower pole shoe 3, or similar ferromagnetic materials can be used as needed.

[0086] The material of kit 4 can be stainless steel or other similar non-magnetic materials. The taper of kit 4 can be the same as that of the lower pole shoe 3, and in order not to affect the sealing effect, kit 4 and vacuum pipe 14 can be welded together.

[0087] The electron beam tube 5 can be made of TA2 or other similar non-magnetic materials.

[0088] The sealing ring 23 can be made of oxygen-free copper or other similar non-magnetic materials. The outer side of the sealing ring 23 is designed to match the taper of the lower pole shoe 3 for positioning. An internal thread can be provided in the groove 39, and an external thread can be provided on the surface of the insertion part 37 of the sealing member 24, so that the sealing ring 23 and the sealing member 24 are connected by threads.

[0089] The sealing component 24 can be made of pure molybdenum / 360 material, and the surface of the insertion part 37 can be provided with multiple airflow holes 38, which connect the gas channel 40 to the first through hole 19. The end of the sealing component 24 away from the sealing ring 23 can be provided with a third through hole 46, which connects to the gas channel 40 through the airflow holes 38.

[0090] For example, three first aperture plates 44 can be provided in the first through hole 19. Similarly, three second aperture plates 45 can be placed in the third through hole.

[0091] The multiple first aperture plates 44 have the same dimensions, with an inner aperture diameter of d1 and a thickness of t1. The multiple second aperture plates 45 have the same dimensions, with an inner aperture diameter of d2 and a thickness of t2.

[0092] Multiple first aperture plates 44 are overlapped and installed in the first through hole 19 of the sealing member 24, and multiple second aperture plates 45 are overlapped and installed in the third through hole 46 of the sealing member 24.

[0093] Figure 11 for Figure 10 A schematic diagram of a cross-sectional view; such as Figure 11 As shown, the number of the first and second apertures is given as an example, and the actual number can be adjusted.

[0094] The number of first apertures installed in the first through-hole 19 essentially determines the pressure difference between the electron beam channel 11 and the transition vacuum region 12. Similarly, the number of second apertures 45 installed in the third through-hole 46 essentially determines the vacuum level in the transition vacuum region 12 and the pressure difference between the working chamber 41 and the working chamber 41.

[0095] Based on the derivation and calculation of formula (1),

[0096]

[0097] P1 is the pressure value (Pa) at the high-pressure (low-vacuum) end;

[0098] P2 is the pressure value (Pa) at the low pressure (high vacuum) end;

[0099] Q is the gas flow rate from the vacuum chamber wall (Pa·L / s);

[0100] C is the flow conductance of the pipeline (L / s);

[0101] L is the air resistance length (mm);

[0102] d is the diameter of the air resistance hole (mm).

[0103] When the vacuum pressure of the vacuum chamber is known, by changing the inner diameter and the number of second aperture plates 45 in the third through hole 46, the vacuum degree of the transition vacuum zone 12 is made higher than that of the working chamber 41.

[0104] Similarly, by changing the inner diameter and number of the first aperture 44 in the first through hole 19, the vacuum level of the electron beam channel 11 is made higher than that of the transition vacuum region 12, thereby meeting the design requirements.

[0105] For example, when the number of second aperture plates 45 in the third through hole 46 is n2, the total length is n2×t2=L2. If n2 is 4 plates and t2 is 0.5mm, then L2 is 2mm, and the inner diameter d2 of the second aperture plate 45 is 1mm. According to experimental test data: when the vacuum value of the working chamber 41 is 700Pa, the corresponding vacuum value of the transition vacuum zone 12 is 5Pa; when the vacuum value of the working chamber 41 is 2.7Pa, the corresponding vacuum value of the transition vacuum zone 12 is 4.8e-2Pa. It can be clearly seen that the vacuum degree of the transition vacuum zone 12 can be two orders of magnitude higher than the vacuum degree of the working chamber 41.

[0106] For example, when the number of first aperture plates 44 within the first through-hole 19 is n1, the total length is n1×t1=L1. If n1 is 6 plates and t1 is 0.5mm, then L1 is 3mm, and the inner diameter d2 of the first aperture plate 44 is 0.4mm. According to experimental test data: when the vacuum value of the transition vacuum region 12 is 1.3e-1Pa, the corresponding vacuum value of the electron beam channel 11 is 9.0e-4Pa; when the vacuum value of the transition vacuum region 12 is 5Pa, the corresponding vacuum value of the electron beam channel 11 is 3.0e-2Pa. It can be clearly seen that the vacuum degree of the electron beam channel 11 can be two to three orders of magnitude higher than that of the transition vacuum region 12.

[0107] In this process, the electron beam is focused onto the sample surface of the stage 42 by the magnetic field generated by the coil 10 within the electron beam channel 11. By changing the current excitation of the deflection coil 10, the magnetic field it generates changes, controlling the deflection motion of the electron beam, thereby enabling it to scan the sample surface.

[0108] Figure 16 This is a schematic diagram of the upper and lower pole shoes in an environmental scanning electron microscope according to an embodiment of the present invention, as shown below. Figure 16 As shown, S is the pole shoe gap; D1 is the upper pole shoe aperture; and D2 is the lower pole shoe aperture.

[0109] Relationship between working distance and resolution: The pole piece structure parameters are designed as follows: S = 4.5 mm, upper pole piece aperture D1 = 24 mm, and lower pole piece aperture D2 = 5 mm. When the working distance is 5 mm, the beam spot diameter is 1.2 nm. When the working distance is 3 mm, the beam spot diameter is 1 nm. When the working distance is 1 mm, the beam spot diameter is 0.86 nm. It is evident that reducing the objective working distance (the distance from the lower pole piece to the sample) can effectively improve SEM imaging resolution.

[0110] In summary, the objective lens 1 and the environmental scanning electron microscope provided in this application can achieve a low vacuum or ambient vacuum working environment for the environmental scanning electron microscope while ensuring the high resolution performance of the objective lens 1.

[0111] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An objective lens, characterized in that, At least including: The upper pole shoe has a connecting part and a working part, the working part having a hollow receiving cavity suitable for forming an electron beam channel; The lower pole shoe is connected to the connecting part, and the working part is at least partially inserted into the lower pole shoe. The area between the inner sidewall of the lower pole shoe and the outer sidewall of the working part forms a transition vacuum zone. A first evacuation hole is provided on the sidewall of the lower pole shoe, which is suitable for evacuating the transition vacuum zone through the first evacuation hole. A sealing structure is disposed at the end of the lower pole shoe away from the upper pole shoe to separate the electron beam channel from the transition vacuum region and to separate the transition vacuum region from the external environment; the sealing structure has a gas channel and a first through hole through which the electron beam passes, the gas channel connecting the first through hole and the transition vacuum region; A gap is left between the end of the working part away from the connecting part and the inner wall of the lower pole shoe to connect the transition vacuum zone and the gas channel; The sealing structure includes a sealing ring and a sealing element; One end of the sealing ring is inserted into the receiving cavity, and the other end abuts against the inner bottom wall of the lower pole shoe; the gas passage is provided on the sealing ring. The bottom of the lower pole shoe is provided with a second through hole, and the end face of the sealing ring facing the second through hole is provided with a groove, and the groove penetrates the other end face of the sealing ring along the height direction of the sealing ring; The sealing member is inserted into the groove through the second through hole, and the first through hole is provided on the sealing member; The sealing element is provided with a third through hole at the end away from the sealing ring, and the third through hole is connected to the gas passage through an airflow hole; An aperture is provided in the first through hole and the third through hole. The vacuum degree between the electron beam channel and the transition vacuum region, and the vacuum degree between the transition vacuum region and the working chamber where the objective lens is located, can be adjusted by adjusting the inner diameter of the aperture and the number of apertures installed to achieve the required pressure difference.

2. The objective lens according to claim 1, characterized in that, The sealing component includes a connected cap and a plug portion; The first through hole passes sequentially through the cap body and the insertion part along the height direction of the sealing member; The plug-in portion is inserted into the groove through the second through hole; The cap is located outside the lower pole boot and abuts against the outer bottom wall of the lower pole boot.

3. The objective lens according to claim 2, characterized in that, A first sealing ring is provided between the cap body and the outer bottom wall of the lower pole shoe.

4. The objective lens according to claim 1, characterized in that, A second sealing ring is provided between the outer wall of the sealing ring and the inner wall of the receiving cavity.

5. The objective lens according to any one of claims 1-4, characterized in that, It also includes an electron beam tube, which is inserted into the receiving cavity, and the end of the electron beam tube located in the receiving cavity extends into the groove, and the lumen of the electron beam tube forms the electron beam channel; Along the irradiation direction of the electron beam, the lumen of the electron beam tube is collinear with the first through hole.

6. The objective lens according to claim 5, characterized in that, A third sealing ring is provided between the outer wall of the electron beam tube and the groove wall of the groove.

7. The objective lens according to any one of claims 1-4, characterized in that, It also includes kits and vacuum tubing; The kit is fitted over the outside of the lower pole shoe, and the open edge of the kit is connected to the open edge of the lower pole shoe by bolts; A second evacuation port is provided on the side wall of the kit at a position corresponding to the first evacuation port. One end of the vacuum pipe is connected to the second evacuation port, and the other end is adapted to be connected to an external vacuum pump.

8. The objective lens according to claim 7, characterized in that, A fourth sealing ring and a fifth sealing ring are provided between the inner wall of the kit and the outer wall of the lower pole shoe, and the fourth sealing ring and the fifth sealing ring are located on different sides of the second air extraction hole along the height direction of the kit.

9. The objective lens according to claim 1, characterized in that, It also includes a support frame, a skeleton, and coils; The bracket has a ring structure and is sleeved on the working part; The inner ring of the bracket abuts against the outer wall of the working part, and the outer ring of the bracket abuts against the inner wall of the lower pole shoe. The area between the side of the bracket facing the sealing structure, the inner wall of the lower pole shoe, and the outer wall of the working part forms the transition vacuum zone. The skeleton is fitted onto the working part, and the skeleton abuts against the side of the bracket that is opposite to the sealing structure. The coil is arranged on the skeleton along the circumference of the skeleton.

10. The objective lens according to claim 9, characterized in that, A sixth sealing ring is provided between the inner ring of the bracket and the outer wall of the working part; A seventh sealing ring is provided between the outer ring of the bracket and the inner sidewall of the lower pole shoe.

11. The objective lens according to claim 9, characterized in that, It also includes a water-cooling structure, including adapters, inlet pipes, and outlet pipes; One end of the water inlet pipe is connected to the water inlet of the frame, and the other end is connected to an external cooling water source through the adapter. One end of the water outlet pipe is connected to the water outlet of the frame, and the other end is connected to an external cooling water source through the adapter.

12. An environmental scanning electron microscope, characterized in that, It includes at least the objective lens according to any one of claims 1-11.

13. The environmental scanning electron microscope according to claim 12, characterized in that, It also includes at least: The workshop, wherein a third exhaust vent and a fourth exhaust vent are provided on the side wall of the workshop; The objective lens extends at least partially into the working chamber, and the vacuum channel on the objective lens is connected to the fourth evacuation port via a pipe. A worktable is disposed within the work chamber and located below the objective lens.

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